In the field of thin film technology requirements for thinner deposition layers, better uniformity over increasingly larger area substrates, larger production yields, and higher productivity have been, and still are, driving forces behind emerging technologies developed by equipment manufactures for coating substrates in the manufacturing of various semiconductor devices. For example, process control and uniform film deposition achieved in the production of a microprocessor directly effect clock frequencies that can be achieved. These same factors in combination with new materials also dictate higher packing densities for memories that are available on a single chip or device. As these devices become smaller, the need for greater uniformity and process control regarding layer thickness rises dramatically.
Various technologies well known in the art exist for applying thin films to substrates or other substrates in manufacturing steps for integrated circuits (ICs). Among the more established technologies available for applying thin films, Chemical Vapor Deposition (CVD) and a variation known as Rapid Thermal Chemical Vapor Deposition (RTCVD) are often-used, commercialized processes.
In semiconductor device manufacturing, various types of plasma processes are used to deposit layers of conductive and dielectric material on semiconductor wafers, and also to blanket etch and selectively etch materials from the wafer. During these processes the wafer is affixed to a wafer chuck in a process chamber and a plasma generated adjacent the wafer surface. Various techniques have evolved to affix the wafer to the wafer chuck. A recent technique for holding the wafer is using an electrostatic chuck.
Electrostatic chucks, which use electrostatic attraction forces to hold a substrate, have several advantages over mechanical and vacuum chucks. For example, electrostatic chucks reduce stress-induced cracks caused by mechanical clamps, allow processing of a larger portion of the substrate, and can be used in processes conducted at low pressures. A typical electrostatic chuck comprises an electrode covered by a dielectric. When the electrode is electrically charged, an opposing electrostatic charge accumulates in the substrate and the resultant electrostatic force holds the substrate onto the electrostatic chuck. Once the substrate is firmly held on the chuck, a plasma of gas is used to process the substrate.
Electrostatic chucks are used for holding a workpiece in various applications ranging from holding a sheet of paper in a computer graphics plotter to holding a semiconductor wafer within a semiconductor wafer process chamber. Electrostatic chucks secure a workpiece by creating an electrostatic attractive force between the workpiece and the chuck. A voltage is applied to one or more electrodes in the chuck so as to induce opposite polarity charges in the workpiece and electrodes, respectively. The opposite charges pull the workpiece against the chuck, thereby retaining the workpiece. In semiconductor wafer processing equipment, electrostatic chucks are used for clamping wafers to a support during processing. The support may form both an electrode (in electrostatic chuck applications) and a heat sink. These chucks find use in etching, chemical vapor deposition (CVD), ion implantation, and physical vapor deposition (PVD) applications.
In an electrostatic chuck, a conductive electrode beneath a dielectric wafer support layer is provided. When a high DC voltage is applied to the electrode, positive and negative charges are respectively produced in the wafer and the electrode, so that the wafer is attracted and held on the chuck surface by the Coulomb force acting between the wafer and the electrode. Plasma etching is performed in this state. When the etching is completed, the supply of RF power and the application of the high DC voltage to the electrode are terminated. Subsequently, the processed wafer is unloaded. The electrostatic chuck eliminates the need for mechanical clamp rings, and greatly reduces the probability of forming particles by abrasion etc., which particles cause yield problems and require frequent cleaning of the apparatus.
One of the problems associated with prior art electrostatic chuck configurations utilized in semiconductor fabrication operations involves the inability of prior art devices to prevent damage to particular parts and elements during movement of the electrostatic chuck from one position to another. For example, during the vertical movement of an electrostatic chuck utilizes in association with a chamber apparatus or semiconductor fabrication system, an associated baffle plate can scratch a chamber wall, resulting in chamber wall polymer peeling.
Thus far, a device or technique has not been developed, which can adequately prevent such scratching and damage during movement of the electrostatic chuck from processing to transfer positions and vice versa. The present inventors thus recognize, based on the foregoing, that a need exists for an apparatus and method, which would prevent such damage. A need also exists for a gauge which can be adapted for use with a semiconductor fabrication system for preventing scratching of a chamber wall by a baffle plate during movement of the electrostatic chuck. The present invention thus was designed by the present inventor to address and meet this important need.